I've only listened for a few minutes as I was more interested in charging the thing, but
as I noted at TMA, the amp has a great stepped attenuator which is balanced evenly even at its lowest setting. And, it has good, sharp edgy mids and bass notes. I am looking forward to getting proper listening done from tomorrow.
Just preliminary, but I decided to test what I was hearing with the hitherto hard-to-drive FitEars 333 and... the Rx performed better than any other portable amp I have tried with the same earphones. Phenomenal actually! While I trust my own ears, I don't absolutely trust my judgement when faced with a 350$ headphone amplifier!